Black ant stings caused by Pachycondyla sennaarensis: a significant health hazard.

Several species of ants cause stings, but not all lead to allergic reactions. We present a series of cases of allergic reactions following insect bites or stings that presented to our emergency department and that were caused by the black samsum ant (Pachycondyla sennaarensis). Reactions ranged from mild allergic reactions to severe anaphylactic shock. Patients were treated with subcutaneous epinephrine 0.3 mg, intravenous methylprednisolone 125 mg, intravenous diphenhydramine HCl 50 mg, and intravenous normal saline as appropriate. These cases illustrate the range of clinical presentations to black ant stings, which can include severe reactions, indicating that ant stings are a significant public health hazard in Saudi Arabia. Physicians in the Middle East and Asia need to be aware of ant stings as a cause of severe allergic reactions.

A llergic reactions, ranging from mild allergic reaction mild hives to severe anaphylaxis and shock, are common presenting problems to emergency departments a well known medical probl l lem facing physicians. Causes have been attributed to drugs, food, contrast agents, exercise and stress, and stings from bees, wasps and ants. 1 Several species of ants are capable of stinging, but not all lead to allergic reactions. Fire ants have been studied thoroughly and are considered responsible for most of allergic reactions secondary to ants in the United States. 2 Systemic reacl l tions with fire ant stings occur in about 4 of 100 000 exposed individuals, and more than 80 fatalities have been reported from fire antlinduced anaphylaxis. 2 In China and Korea another species of ant known as Bachycondayla chinensis is a major cause of allergic reacl l tions. In addition, Myrmecia pilosula (jack jumper ant) in Australia is a known health hazard. 1l3 We have noted a significant number of unidentified insect exposures in our emergency department that have led to different degrees of allergies. Therefore, we decided to identify the cause of these stings or bites by obtaining samples of the causal agent for identification. In this study we selected a case series of patients that were able to identify the cause of the sting as a black ant. The black ant specimens were selected carefully for photography and identification. The identification was Several species of ants cause stings, but not all lead to allergic reactions. We present a series of cases of allergic reactions following insect bites or stings that presented to our emergency department and that were caused by the black samsum ant (Pachycondyla sennaarensis). Reactions ranged from mild allergic reactions to severe anaphylactic shock. Patients were treated with subcutaneous epinephrine 0.3 mg, intravenous methylprednisolone 125 mg, intravenous diphenhydramine HCl 50 mg, and intravenous normal saline as appropriate. These cases illustrate the range of clinical presentations to black ant stings, which can include severe reactions, indicating that ant stings are a significant public health hazard in Saudi Arabia. Physicians in the Middle East and Asia need to be aware of ant stings as a cause of severe allergic reactions.
done by a certified entomologist in the Department of Zoology, College of Science, King Saud University in Riyadh. All the specimens were collected from the eastl l ern region of Riyadh in year 2006l2007. The species was then identified and its characteristics were described. The cases we report are cases that we encountered durl l ing our practice, ranging from mild to severe allergic rel l action secondary to these black ant bites (Table 1). We note that the cases ranged from mild to severe allergic reaction requiring epinephrine. We also present a sugl l gested treatment and followlup algorithm.

Case 1
A 34lyearlold Saudi male presented to the emergency department complaining of generalized body rash and itching starting 30 minutes after being stung by a black ant at home. He had no other complaints such as shortl l ness of breath, lightheadedness, chest pain or palpital l tions. He had no previous medical or surgical history and was not known to be allergic to any medication, food or any other allergen and never had an allergic rel l action in the past. On examination he displayed normal vital signs and had a pruritic, urticarial rash over the four limbs and trunk. The patient was given methyll l prednisolone 125 mg and diphenhydramine HCI 50 mg intravenously and kept in the ER observation area for four hours until his symptoms started to subside and then he was discharged home with instructions on how to avoid future ant bites.

Case 2
A 27lyearlold Saudi female presented one hour after being stung by a black ant at her neighbor' s home. She complained of an itchy rash and lightheadedness. These complaints started minutes after being stung. She had no medical history or allergic reactions in the past. Her initial vital signs were a blood pressure of 105/75 mm Hg, a heart rate of 99 per minute, a respiratory rate of 22 per minute, a temperature of 36.6°C and an oxygen saturation of 98% on room air. After 15 minutes of prel l sentation the patient complained of dizziness and her blood pressure dropped to 77/44 mm Hg. The patient had a generalized urticarial rash mainly over the upper limbs and abdomen. The rest of her physical examinal l tion was unremarkable. She was managed by 0.3mg subcutaneous epinephrine and a bolus of 1 liter of norl l mal saline after which her blood pressure returned to normal. She was given methylprednisolone 125 mg and diphenhydramine HCI 50 mg intravenously and was observed in the emergency department for four hours and then discharged home in stable condition.

Case 3
A 27lyearlold Saudi female presented to our emergenl l cy department with a chief complaint of breathlessness, dizziness and itching and redness over the body after an ant sting 2 hours prior to presentation. Symptoms started about 5 minutes after the sting. Her medical history included allergic rhinitis. Physical examination showed an anxious and restless woman with stable vil l tal signs and generalized urticaria (Table 1). She was managed by intravenous fluid therapy, subcutaneous epinephrine injection, methylprednisolone 125 mg and diphenhydramine HCI 50 mg intravenously. After obl l serving her for six hours, she was discharged in good condition.

Case 4
A 49lyearlold Saudi female presented to our departl l ment after a black ant sting, complaining of shortness of breath and generalized swelling, mainly of the face and lips along with an itchy rash that started 10 minutes after being stung by a black ant at her home. This was the sixth presentation for this patient to our departl l ment suffering from anaphylaxis secondary to a black ant stings. Her medical history included a cirrhotic livl l er secondary to hepatits C virus infection. Initial vital signs were normal with wheezing evident on chest ausl l cultation (Table 1). However, the patient became more distressed and the swelling increased and her level of consciousness deteriorated rapidly, so the patient unl l derwent endotracheal intubation. The team intubating her faced a difficult intubation. They only managed to insert a 6.5 mm endotracheal tube due to airway edema. She was started on epinephrine infusion, methylpredl l nisolone 125 mg and diphenhydramine HCI 50 mg inl l travenously. She was admitted to the intensive care unit    for two days, and after extubation she was observed on the floor for another two days. She was discharged with an EpiPen kit and strongly advised not to walk barel l foot and to perform pest control and eradication in her house and its surroundings.

DIsCUssION
Pachycondyla sennaarensis belongs to the subfamily Ponerinae, a species that is widely distributed in tropil l cal and subtropical regions worldwide. It is believed to be indigenous to Southeast Asia, but has been reported from all of the Arab Gulf countries including Kuwait, Qatar, the United Arab Emirates, Oman, Yemen and Saudi Arabia. 4 In Saudi Arabia it seems to prefer areas of human habitation. Although the ant is a scavenger in nature, it stings human beings as a defensive behavl l ior. 5 Recently, several anaphylactic cases following black (samsum) ant stings were reported in local clinics in Saudi Arabia, some of them critical. 6 This ant has been observed around and inside houses and in hospital resil l dence areas in many locations in the Al Riyadh region. The risk to humans from a particular species probably depends on complex interactions between the likelil l hood of human contact, insect aggression, efficiency of the venom delivery apparatus, and venom allergenicity. RefeRences pit, and the presence of a deep mesopropodal furrow ( Figure 1). It does not bite; instead, it injects venom through a stinger (Figure 2), like fire ants and other Hymenoptera. The mechanism of the reaction to the sting of the black ant Pachycondyla sennaarensis is a type I IgElmediated hypersensitivity and the diagnosis can be confirmed by skin tests and specific IgE deterl l mination. 7,8 The imported fire ant is a significant health probl l lem in the southern United States. 2 The venom from fire ants contains several allergenic proteins, which can cause anaphylaxis in allergic individuals. The safety and effectiveness of several immunotherapy options have been documented for fire ant stings. 9,10 However, research has shown that patients who have had an anal l phylactic reaction to a Pachycondyla species ant might not benefit from immunotherapy with an imported fire ant extract. 10 Immunotherapy with the extract of Pachycondyla species ants is expected to be highly effecl l tive. Ant venom immunotherapy is feasible and highly efficacious. 10 However, the limited geographical distril l bution of each species presents a major challenge to making venom extracts available for clinical use. 12 In this study we confirmed the exact species, the venomous nature of its sting and the range of clinical manifestations associated with black ant stings. The acute emergency treatment depends on the manifestal l tion that develop. The acute treatment is summarized in Figure 3. Patients need to be followedlup by AN iml l munologists for these cases to be managed appropriatel l ly and to document if they develop secondary reactions. The cases were referred to primary health care in this case series prior to documenting that the cause of the allergy was an ant bite.
The study of ant allergy in Asia and the Middle East is in its infancy. Clinicians in these countries need to be aware of ant stings as a cause of severe allergic reactions. Certain species that cause allergic reactions deserve further research. The allergens in the venom of the different ant species need to be identified. We should aim for improved understanding of the epidel l miology of antlsting anaphylaxis, formulation of betl l ter diagnostic tests and possibly the introduction of immunotherapeutic strategies. We believe these types of studies are required to find an effective treatment or prophylaxis against ant stings as it is a health hazard that can lead to severe morbidity and mortality. This study confirms that public health problems due to sel l vere ant sting anaphylaxis in this region are due to the ant species Pachycondyla sennaarensis (samsum ant).